App Store policies, in-app video ads, and dark matter deductions

There have been some stories recently about Apple rejecting apps that contain video ads encouraging people to watch them or share them in exchange for in-app rewards. No doubt this was worrisome to the advertising agencies and developers involved in those apps, but some of the theories as to what exactly was happening tended towards the overly complex, and in some cases, conspiratorial. Tim Cook famously said that, when it comes to Apple hardware plans, looking at one piece of supply chain data didn't allow for the drawing of any meaningful conclusions. Likewise, looking at ad network complaints and developer reactions doesn't necessarily allow for any useful insight into App Store policies. That appears to be the case here as well. So, what exactly has been going on?